Basically, you would type the command and then click a shop sign. It would tell you if you could buy or sell from that chest shop. Potential uses: Confirming that your own chest shop is set up correctly and the item can be bought/sold. Knowing the price of commodities at exchanges, which is useful for planning of your own pricing strategy. Knowing if a given item is in stock at a store without having to spend money. This is particularly useful if the item is expensive and you are comparing prices. Knowing if you will be able to sell something on another server before you actually use the vault to move it across. Those are just a few examples. There may be other use cases I didn't think of. I also think it may be useful to have a residence flag which allows users to also be able to view the stock level. If the flag is set, they can see how many items are available and how much room there is to sell items. If the flag is not set, they only know whether they can buy/sell but no quantities.
I make a LOT of money off of the few shows that display their stock using redstone lamps. It's a bad idea for the shops to display this information, since keeping stock secret is a valid market strategy.
It's good for shop owners, and for traders. As a trader, if I knew when shops were out of stock, I could trade until all the cheap shops were totally empty, and the expensive shops were totally full (This is what I do to the shops that provide this information) Eventually the cheap shops would raise prices, and the expensive shops would lower prices. This could lead to a leveling of the market, where all trading is margin trading at best. Sure I'd make a ton of money at first, but then it would level off and make trading pointless, I'd just sell to the first shop I find because they'd all be about equal price (to avoid quickly selling out, or quickly filling up and selling nothing). No competition makes the shop owners all get bored, and move off to something else
I've been frustrated before by my inability to not view the contents of Chests for various reasons, mainly while trying to help someone stock a shop where I did not have Chest permissions and while trying to evaluate pricing for shops. You want to have a competitive price, yet you do not want to compete with an empty chest and buying that item does not really help since you really do not know what is in there until you have emptied it. I'd like to see something like this, but It seems that there should be a better way than typing a command. We have had the suggestion before to allow players to peek inside Chests. Not sure how hard or easy that would be to program but it would give us the information we need. Maybe we could have the number of units left on the Shop Sign, or the lettering could change colors from Red to Orange, Yellow, Green... to show the percentage of the item as a ratio to Storage space(not sure whether we would want to ignore Dirt or other fillers). Possibly we could use a specific item, like a renamed Stick to click on a Sign something like String does. That could be a very popular and useful Promo item.
As a trader, you already do know when shops with low prices are out of stock. Just try to buy. There's no real risk because you want to buy the low-priced item anyways. In fact it would be slower for a trader to use the command. I don't feel that shop owners would get bored, or that competition would be eliminated. Shop owners still fight for having the cheapest price and the highest payout. As owning a shop has an inherent risk of left over stock, and requires a significant investment of time, no shop is going to accept 0 commission, so they will still have a margin. So even if your premise holds and all the arbitrage opportunities between shops disappear, I don't understand how that's a problem for shop owners. Shop owners will still compete for finding cheaper and cheaper ways to produce goods, so they can get more sales, and also compete to pay more and get suppliers. There are still a lot of strategies. The only difference for a shop owner is perhaps less frustration with having all their items bought/sold at once.
